Fix coverage on CI

tests/test_cli.py

@@ -117,17 +117,19 @@ class TestArgumentParsing:
         nb_path = tmp_path / "nb.ipynb"
         nb_path.touch()
         nb_path.chmod(0)
-        if os.access(nb_path, os.R_OK):
-            pytest.skip("failed to make file unreadable")  # pragma: no cover
 
-        result = runner.run(nb_path)
+        if os.access(nb_path, os.R_OK):  # pragma: no cover
+            # doesn't work on CI due to Docker weirdness
+            pytest.skip("failed to make file unreadable")
+        else:  # pragma: no cover
+            result = runner.run(nb_path)
 
-        msg = f"Invalid value for 'NOTEBOOK': File '{nb_path}' is not readable."
-        expected.usage_lines()
-        expected.error_panel(msg)
-        expected.exit_code = 2
+            msg = f"Invalid value for 'NOTEBOOK': File '{nb_path}' is not readable."
+            expected.usage_lines()
+            expected.error_panel(msg)
+            expected.exit_code = 2
 
-        expected.check(result)
+            expected.check(result)
 
 
 def test_wrong_location(